Print Environment
Variables
#include
#include
void main(int argc, char *argv[], char * envp[])
{
int i;
for (i = 0; envp[i] != NULL; i++)
{
printf("\n%s", envp[i]);
}
}
Output
HOSTNAME=localhost.localdomain
SELINUX_ROLE_REQUESTED=
SHELL=/bin/bash
TERM=xterm
HISTSIZE=1000
SSH_CLIENT=192.168.7.43 49162 22
SELINUX_USE_CURRENT_RANGE=
QTDIR=/usr/lib64/qt-3.3
QTINC=/usr/lib64/qt-3.3/include
SSH_TTY=/dev/pts/8
USER=harika
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lz=01;31:*.xz=01;31:*.bz2=01;31:*.tbz=01;31:*.tbz2=01;31:*.bz=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.rar=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
PATH=/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/home/harika/bin:.
MAIL=/var/spool/mail/harika
PWD=/home/harika
KDE_IS_PRELINKED=1
LANG=en_US.UTF-8
KDEDIRS=/usr
SELINUX_LEVEL_REQUESTED=
HISTCONTROL=ignoredups
SSH_ASKPASS=/usr/libexec/openssh/gnome-ssh-askpass
HOME=/home/harika
SHLVL=2
LOGNAME=harika
CVS_RSH=ssh
QTLIB=/usr/lib64/qt-3.3/lib
SSH_CONNECTION=192.168.7.43 49162 192.168.7.140 22
LESSOPEN=|/usr/bin/lesspipe.sh %s
G_BROKEN_FILENAMES=1
_=./a.out
OLDPWD=/home
Copy File into Another
File
#include
#include
void main(int argc,char **argv)
{
FILE *fp1, *fp2;
char ch;
int pos;
if ((fp1 = fopen(argv[1],"r")) == NULL)
{
printf("\nFile cannot be opened");
return;
}
else
{
printf("\nFile opened for copy...\n ");
}
fp2 = fopen(argv[2], "w");
fseek(fp1, 0L, Seek_End);
pos = ftell(fp1);
fseek(fp1, 0L, Seek_Set);
while (pos--)
{
ch = fgetc(fp1);
fputc(ch, fp2);
}
fcloseall();
}
Output
File opened for copy...
$cmp /tmp/vmlinux mylinux
$ ls -l mylinux
-rw-rw-r--. 1 adi adi 3791744 Jul 27 19:57 mylinux
Create Employee Record
and Update it
#include
#include
#include
#include
#define size 200
struct emp
{
int id;
char *name;
}*emp1, *emp3;
void display();
void create();
void update();
FILE *fp, *fp1;
int count = 0;
void main(int argc, char **argv)
{
int i, n, ch;
printf("1] Create a Record\n");
printf("2] Display Records\n");
printf("3] Update Records\n");
printf("4] Exit");
while (1)
{
printf("\nEnter your choice : ");
scanf("%d", &ch);
switch (ch)
{
case 1:
fp = fopen(argv[1], "a");
create();
break;
case 2:
fp1 = fopen(argv[1],"rb");
display();
break;
case 3:
fp1 = fopen(argv[1], "r+");
update();
break;
case 4:
exit(0);
}
}
}
void create()
{
int i;
char *p;
emp1 = (struct emp *)malloc(sizeof(struct emp));
emp1->name = (char *)malloc((size)*(sizeof(char)));
printf("Enter name of employee : ");
scanf(" %[^\n]s", emp1->name);
printf("Enter emp id : ");
scanf(" %d", &emp1->id);
fwrite(&emp1->id, sizeof(emp1->id), 1, fp);
fwrite(emp1->name, size, 1, fp);
count++; // count to number of entries of records
fclose(fp);
}
void display()
{
emp3=(struct emp *)malloc(1*sizeof(struct emp));
emp3->name=(char *)malloc(size*sizeof(char));
int i = 1;
if (fp1 == NULL)
printf("\nFile not opened for reading");
while (i <= count)
{
fread(&emp3->id, sizeof(emp3->id), 1, fp1);
fread(emp3->name, size, 1, fp1);
printf("\n%d %s",emp3->id,emp3->name);
i++;
}
fclose(fp1);
free(emp3->name);
free(emp3);
}
void update()
{
int id, flag = 0, i = 1;
char s[size];
if (fp1 == NULL)
{
printf("File cant be opened");
return;
}
printf("Enter employee id to update : ");
scanf("%d", &id);
emp3 = (struct emp *)malloc(1*sizeof(struct emp));
emp3->name=(char *)malloc(size*sizeof(char));
while(i<=count)
{
fread(&emp3->id, sizeof(emp3->id), 1, fp1);
fread(emp3->name,size,1,fp1);
if (id == emp3->id)
{
printf("Enter new name of emplyee to update : ");
scanf(" %[^\n]s", s);
fseek(fp1, -204L, SEEK_CUR);
fwrite(&emp3->id, sizeof(emp3->id), 1, fp1);
fwrite(s, size, 1, fp1);
flag = 1;
break;
}
i++;
}
if (flag != 1)
{
printf("No employee record found");
flag = 0;
}
fclose(fp1);
free(emp3->name);
free(emp3);
}
Output
1] Create a Record
2] Display Records
3] Update Records
4] Exit
Enter your choice : 1
Enter name of employee : aaa
Enter emp id : 100
Enter your choice : 1
Enter name of employee : bbb
Enter emp id : 200
Enter your choice : 1
Enter name of employee : ccc
Enter emp id : 300
Enter your choice : 1
Enter name of employee : ddd
Enter emp id : 400
Enter your choice : 1
Enter name of employee : eee
Enter emp id : 500
Enter your choice : 2
100 aaa
200 bbb
300 ccc
400 ddd
500 eee
Enter your choice : 3
Enter employee id to update : 300
Enter new name of emplyee to update : cdefgh
Enter your choice : 2
100 aaa
200 bbb
300 cdefgh
400 ddd
500 eee
Enter your choice : 4
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